Method Atlas · Axial compression
Every code, mapped against reality.
Codes report a single knockdown; MDC computes it from the physics. Here is the difference resolved over geometry — pick a design code and see exactly where it wastes steel, and where real welded tests buckle below it. Coloured by the same collapse experiments, not model-vs-model.
σMDC / σcode — capacity ratio
Heavy rule = λ̄ ≈ 1 (R/t ≈ 358 @ S355): above elastic (imperfection-governed) · below plastic (yield-governed).
L / R — length ratio →
Colour = ratio; dark line = 1.0 (parity). Red = below 1 (code non-conservative), blue = MDC recovers capacity.
Real tests
• each dot = one collapse test at its measured imperfection
red, below 1 = the shell buckled under the prediction
Axial compression, S355 heatmap. MDC knockdown factors are FEM-calibrated; the code curves are the published rules. Same imperfection basis where the code allows it (EN Class C). R/t = wall slenderness, L/R = length ratio, Z = Batdorf parameter.